Composite fluid flowmeter with slotted arcuate axial exhaust

ABSTRACT

A composite tangential and axial exhaust fluid flowmeter featuring both tangential and balanced, bidirectional axial exhaust outlets cooperating with a common tangential inlet to a fluid chamber, which encloses a minimum mass of fluid and has an escalloped peripheral wall surrounding a light weight, low mass multi-toothed rotor freely rotatably mounted in the fluid chamber. The axial exhaust outlets are constituted by an arcuate shaped slotted opening in the side wall of the fluid chamber and in the cover element enclosing the chamber.

BACKGROUND OF THE INVENTION

This invention relates to fluid flowmeters, and, more particularly, toan improved fluid flowmeter transducer device specially suited for usein engine fuel consumption and/or management systems for combustionpowered engines.

An example of a fuel metering system in which the herein describedflowmeters may be employed is illustrated by U.S. Pat. No. 4,048,964,which requires a fuel flowmeter transducer device developing a pulsatoryelectrical signal whose pulse repetition rate varies linearly inaccordance with the flow rate of fuel supplied to the engine. Airsupplied to the engine is sensed by a swirl-type air flowmeter whosepulsatory electrical signal output is processed together with the fuelsignal pulses from the fuel flowmeter by a mass fuel/air ratio scheduledelectronic controller, which controls a fuel metering or supply deviceto supply fuel to the engine precisely in accordance with the scheduledfuel/air ratio.

The abovementioned fuel metering system is intended to meet stringentengine emission and fuel economy mandates for production vehicles andrequires, for its successful implementation, precise and reliableinstruments possessed of a high degree of accuracy and linearity overthe entire range of engine performance and vehicle operating conditions.In addition to a low pressure drop, the fuel flowmeter or flowtransducer device should produce a high pulse count output at low fuelflow rates, as during engine idle conditions, and should also exhibit afast response to fluid flow rate changes as well as a rapid run-down orbraking characteristic when the fluid flow therethrough has beendecreased, as during vehicle deceleration conditions. Consistent andoptimum performance and repeatability of results between productionflowmeters are also necessary criteria.

Known forms of prior art flowmeters, as exemplified by U.S. Pat. Nos.3,329,021; 3,867,840; and 4,047,433, for example, fall short of meetingthe foregoing requirements.

The present invention thus seeks generally and has among its objects toprovide a fuel flowmeter transducer device possessed of the aboveenumerated and other desirable characteristics and which is of compactsize, composed of a minimum number of parts and is of simple andinexpensive construction suited to high volume production fabrication.

SUMMARY OF THE INVENTION

According to the present invention there is provided a relatively smalland compact fluid flowmeter whose output is linearized by combining thecharacteristics of both tangential and axial type flowmeters. Thecomposite flowmeter features separate tangential and balanced,bidirectional axial exhaust outlets cooperating with a common tangentialinlet to an enclosed fluid chamber, which is of minimum volumetriccapacity and encloses a minimum mass of rotating fluid. The fluidchamber has an escalloped peripheral wall surrounding a light weight,low mass multi-toothed rotor, which is freely rotatably mounted in thefluid chamber on a self-centering spindle providing a line contact andlow frictional coefficient engagement along the full axial width of therotor hub closely fitting thereon.

The rotational rate of the rotor is sensed by a photoelectric opticaltransducer system, which produces a pulse count for each rotor toothpassing thereby and is supported in a pressed-in, integral insulativemounting and connector clip, which is readily mountable to andaccessible from the exterior of the meter housing without disassembly ofthe flowmeter.

The meter housing is readily attachable to and pluggably receivable as astopper in the cylindrical bore of an outlet chamber cavity in the fuelpump housing into which fluid is exhausted from the plurality offlowmeter outlet ports. The flowmeter body carries on the outer side ofthe stopper portion thereof an attachable or housing for electroniccircuitry for the photoelectric transducer system, which is connected tothe electronic circuitry through connector pins carried in the mountingfor the photoelectric transducer elements.

The foregoing and other objects, features and advantages of the severalaspects of the invention will be more fully understood from the detaileddescription following and made with reference to the accompanyingdrawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view with parts broken away of an electricmotor driven, fuel metering pump incorporating the flowmeter of thepresent invention;

FIG. 2 is an enlarged side elevational view of a flowmeter in accordancewith the invention;

FIGS. 3 and 4 are end views taken in the directions 3--3 and 4--4,respectively, of FIG. 2;

FIG. 5 is a cross-sectional view taken in the plane 5--5 of FIG. 3 ofthe flowmeter housing with the rotor assembly and photoelectrictransducer assembly removed;

FIG. 6 is a further enlarged sectional view with parts broken away takenin the direction 6--6 of FIG. 3;

FIG. 7 is a view similar to FIG. 6 of a part of the flowmeter housing;

FIG. 8 is a side elevation view of the rotor of FIG. 7;

FIG. 9 is a side elevation view of an integral mounting for thecomponents of the photoelectric transducer employed with the flowmetersherein;

FIG. 10 is an enlarged side elevational view of a flowmeter housing inaccordance with another embodiment of the invention; and

FIG. 11 is a characteristic curve of a flowmeter utilizing theprinciples of the present invention.

DESCRIPTION

Referring to the drawings, FIG. 1 illustrates to approximate scale anelectric motor driven fuel pump 20 designed for use in the fuel meteringsystem of the aforementioned U.S. Pat. No. 4,048,964 to deliver ascheduled quantum of fuel whose mass flow rate is continuously monitoredby the flowmeter 40 of the present invention.

The pump 20, which is of the slipper variety, delivers fuel to theengine (not shown) at a relatively high pressure, say, 60 psi at maximumflow rates for example, and has a cover or end housing 22 into whichfuel is admitted to an inlet 23 and which contains an outlet passage 24communicating with a bored cylindrical outlet chamber 25. The subjectflowmeter 40 is received within the open end of the bored chamber,abutting against the end wall 26 thereof, and has an annular groovedheader or plug stopper portion 42 at the other end thereof which carriesan O-ring 44 in the annular rim 43 thereof and is of a diameter as toeffectively seal the open end of the pump outlet chamber.

Fuel flows outwardly through a plurality of exhaust ports, which areformed in the sides of the flowmeter and are more fully describedhereinafter, in the directions indicated into the outlet chamber 25 inthe pump end housing or cover from which it exhausts through pump outletpassages 28 and 29. Removably attached to the header 42 at the outer endof the meter housing is a flanged, rectangular plastic housing 100,which is releasably fastened to the pump cover and contains theelectronic circuitry for the photo-optical transducer system associatedwith the flowmeter.

With reference to the flowmeter embodiment shown in FIGS. 2-9 of thedrawings, the flowmeter 40 includes a one-piece headed T-shape, die-castzinc housing 41, which is formed with the aforementioned cylindricalheader 42 at one end thereof and a short, longitudinally extendingblock-shaped body portion 50, which is of a rectangular cross-sectionand stems or projects normally from the back face of the header. Formedin the body portion 50 is a cylindrical cavity 51, which opens to and isaccessible from one side of the body portion and extends therein a depthor distance to the bottom or side wall 52 of the cavity that is slightlymore than one-half the thickness or width of the body portion withreference to the orientation of the meter shown in FIG. 3.

As shown in FIGS. 5, 6 and 7, the cavity is of stepped formation with aninwardly tapering circumferential wall 54 surrounding a diametricallyreduced, inner circumferential wall 55, which is joined to the wall 54by a circumferential land portion 56. Cast in the land portion is aplurality of arcuate or scallop-shaped, broad or flat-tipped brakingteeth 57 formed by substantially uniformly spaced, inwardly extendingarcuate pockets 58 of a depth or radius approximately one-third theradius of the cavity.

Closing the opening and seating against the escalloped peripheral orcircumferential land 56 in the cavity is a one-piece, die-cast, steppedcover 70 having a plurality of openings therein and an integrallyformed, radially extending alignment tab 71, which is received in acomplimentary depression in the cavity opening side of the meter bodyportion. An O-ring 72, carried on the diametrically reduced portion 74of the stepped cover, centrally aligns and seals the cover against thebody portion to which it is removably fastened by threaded screws 73.

Fluid is admitted to the narrow fluid chamber 60, which is providedbetween the inner face of the cover 70 and the bottom side wall 52 andthe reduced cylindrical portion 55 of the cavity in the body portion,through an inlet passage 61, which is formed in the lower section and inthe longitudinal axial central plane of the body portion. The inletorifice has a flared or bell-shaped inlet opening 62 at the outer end ofthe meter housing, which abuts against the end wall 26 of the boredcylindrical chamber 25 in the pump cover 22 and is sealed thereagainstby an O-ring sealing element 30 surrounding the pump outlet passage 24,as shown in FIG. 1. At its outer end, the flared inlet opening 62 has adiameter approximately three times that of the inlet passage 61, whichextends longitudinally of the body portion 50 and intercepts theperipheral circumferential wall 55 of the fluid chamber 60 tangentiallyof and in the southwest quadrant of the cavity, as shown in FIG. 5. Theflared inlet provides a smooth transition to the fluid flow from thepassage 24 to the tangential inlet orifice, which is of a reduceddiameter, and minimizes any tendency to the production of turbulence.

Cast in the lower portion of the housing body 50 and colinear to thelongitudinal axis of the tangential inlet passage 61 is a tangentialoutlet passage 63, which is in this configuration, of substantially thesame diameter as the inlet passage. Outlet passage 63 extendslongitudinally through the housing body portion 50 and a concavity 45 inthe header 42, which receives a sealing plug 46 cemented in the cavityfor blocking the end of the outlet passage remote from the fluid chamber60. The tangential outlet passage 63 communicates with a generally bootor shoe-shaped slot 64, which is cast in and extends the width ortransversely through the body portion, to exhaust fluid from thetangential outlet passage 63 through both sides of the body portion intothe cylindrical outlet chamber 25 in the pump cover or end housing.

In addition to the outlet passage 63, which exhausts fluid tangentiallyof the fluid chamber 60, fluid is also exhausted generally axially ofthe fluid chamber through outlet openings formed in and extendingthrough the side wall 52 of the cavity 51 and axially of the cover 70.In the embodiment illustrated in FIGS. 2-9, the axial exhausts areformed by a series of six equally spaced holes 65, each measuringapproximately 0.030 inch in diameter. The holes 65 are distributed alonga substantially semicircular arc, which is located above the tangentialinlet and outlet passages at a radial distance from the geometricalaxial center of the fluid chamber approximately two-thirds of the radiusof the chamber and is oriented to include the northwest and part of thenortheast and the southwest quadrants of the cavity 51. An axial exhaustprovided by a similar set of holes 75, which are axially aligned withthe outlet holes 65 in the side wall 52 of the cavity, is provided inthe cover 70.

Located radially inwardly of the axial exhaust outlet holes in thecavity side wall 52 and in the cover 70 is an integrally formed,centrally located hub 66, 76, formed on the inner face of the cavityside wall and on the cover respectively. Each of the hubs has a boredaperture 67, 77 extending partly therethrough as shown in FIGS. 6 and 7for receiving one end of a solid uniform section pin or spindle 81,which has a close, but loose and not necessarily a press, fit thereinand on which is mounted the rotor element 80. At their outermost ends atthe surface of the cavity end wall 52 and inner face of the cover, theapertures 67, 77 are countersunk as shown at 68 (FIG. 7) to form conicalguides, which aid in centering and positioning the spindle when thecover 70 is assembled to the housing 41 with the spindle and rotorassembly in place therein.

Rotor 80 is molded in one piece of a light weight material, which isinert to the fluid (gasolene) passing through the flowmeter and has aspecific gravity slightly greater than, but ideally approaching that ofthe fluid. Structurally, it includes the aforesaid axial hub 82, a thincircular web portion 83 and a thicker rim portion, around the peripheryof which are distributed eight equally spaced teeth 85, which are ofuniform, substantially equal width and depth and of an axial thicknessslightly less than that of the rotor hub 82, as shown in FIG. 8.

Spindle 81 is constructed of a material inert to the metered fluid, asnon-corrosive stainless steel nickel alloy music wire, of a diameter ofa few thousandths of an inch, 0.0015 for example, smaller than that ofthe diameter of the closely fitting rotor hub 82, the central bore ofwhich has a die smooth internal finish. The rotor wheel is thus freelyrotatable on or relative to the spindle, which provides a fine linecontact engagement with and along the full axial width of the lowfriction coefficient rotor hub. Nylon, impregnated with Teflon fibers,has been found to satisfy the above enumerated requirements for thecomposition of the rotor wheel providing a light weight, low mass andinertia, chemically inert, dimensionally stable structure, althoughother plastic combinations suitable to the application, could be found.Its unitary journal and mounting arrangement on the relatively fixed ornon-rotating spindle provides a low friction mount, comparable to thatprovided by costlier jeweled journals. Ball race bearings employed inprior forms were obviated due to their added inertia, extra cost andadditional assembly procedures. The side faces of the rotor wheel may besand blasted or otherwise roughened or treated to provide a matte,flocked, stippled, pimpled or dimpled surface finish thereon, which hasbeen found to yield some improvement in the cogging effect between therotor and the viscosity of the fluid, thereby improving the linearitycharacteristic of the meter.

The rotation of the rotor is sensed by the photoelectric transducerassembly 90 comprising a photo-diode 91 and a phototransistor 92, whichare supported in a generally U-shaped, unitary mounting 93 molded inone-piece of a plastic insulator material, as Nylon for example,chemically inert to the metered fluid. Mounting 93 encircles theflowmeter housing on three sides, i.e., the bottom and both sides, asshown in FIG. 3 and has a pair of laterally-spaced, integrally formedarms 94 extending normally from its front face. Each arm 94 has a split,inwardly-directed, apertured protuberance or projection 95, whichreceives one of the photodiode 91 and phototransistor 92 elements asshown in FIG. 6, and is press-fitted snugly in place into a countersunkaperture 69, 79 provided in the cavity sidewall 52 and cover 70, asshown. The apertures 69, 79 are positioned, and are of such dimension attheir reduced innermost ends, so that the radiant energy beam from thephotodiode 91 and incident upon the phototransistor 92 will be in thepath of and will be intercepted by the rotation of the rotor 80. Thus,the width of the rotor teeth should be greater than the diameter of thereduced inner ends of the countersunk apertures 69, 79 and the width ofthe radiant energy beam so that the latter will be completely occludedand periodically interrupted by the passage of the rotor teeth thereby.

The electrical leads from the photodiode and phototransistor elementsextend outwardly of the mounting projections 95 and are soldered to thesplit or tined ends of a respective one of four electrically conductiveconnector pins 96 formed of brass material. Connector pins 96 arereceived in four longitudinally extending protuberances 97, which areintegrally formed on the plastic mounting 93 and are received in andextend through a different and corresponding one of four similarlyspaced, rectangularly arrayed, axially extending openings 47 in theheader 42. Each pin 96 has an enlarged short cylindrical section 98approximately midway of its length just beyond the point where it exitsfrom the front face of the header 42 and carries an O-ring 99 positionedbetween the cylindrical section 98 and the front face of the header 42to seal the opening 47 in which it is carried in the header. The outerends of the connector pins 96 pass through the outer wall into theinterior of the aforementioned plastic housing 100, which forms anelectrical plug-type attachment and connector with the connector pinsand is detachably mechanically fastened to the header 42 by a threadedstud (not shown), received in a threaded opening 48 located centrally ofthe header.

FIG. 10 illustrates another embodiment of a flowmeter, which isgenerally similar to that described and shown in FIGS. 2-9 herein,except for the configuration of the axial exhausts, which have beenopened up and enlarged to improve the linearity of the flowmeter. InFIG. 10, the axial exhaust outlets are formed as arcuate, slot-shapedopenings 65' and 75' in the cavity side wall 52 and cover 70, thelongitudinal arcuate axis of the slots being displaced radially from thecenter of the cavity by a distance approximately two-thirds of theradius of the chamber 60 or one-half of the radius of the stepped cavity51. With reference to the vertical orientation of the flowmeter, theslots are located in a region past the tangential outlet port 63 in thedirection of rotation of the fluid around the cavity or in the third andfourth or northeast and northwest quadrants thereof.

In a preferred form of the flowmeter exhibiting low drift, excellentlinearity and optimum repeatability characteristics, the slot spans anarc of approximately 95 degrees or slightly greater than one quadrant ofarcuate length or extent and has a width, taken in a radial direction,of approximately 0.067 inch, with tangential inlet and tangential outletorifice diameters of 0.067 inch and 0.070 inch, respectively. A 0.067inch slot of an arc length of 123 degrees has also been employed withtangential inlet and outlet orifice diameters of 0.063 and 0.067 inch,respectively.

From the foregoing dimensions it can be seen that the flowmetersdescribed herein are of extremely compact size and miniatureconstruction. The inner diameter of the stepped cavity 51 in theflowmeter housing measures 0.500 inch and the fluid chamber 60, which isof a width of 0.094 inch, encloses a minimum volume of fluid therein.Thus, the rotating volume of fluid within the chamber 60 will be ofminimum mass and inertia so that the flowmeter will accurately andrapidly respond to changes in the fluid flow therethrough. The elevationand location of the rotational axis of the rotor wheel relative to thetangential inlet orifice in the depicted orientation of the flowmeterprovides buoyant support to the rotor by incoming fluid. The abovefactors taken in further conjunction with the low friction mounting ofthe light weight, low mass miniature rotor wheel 80 in the fluid chamberand the braking teeth 57 provided in the peripheral circumferential wall55 of the chamber contribute to the fast response and rapid brakingcharacteristics of the subject flowmeters.

FIG. 11 is a semi-logarithmic plot of the linearity characteristic ofthe flowmeter of FIG. 10 and represents the slope of the flowmetercalibration curve (not shown) over the range of fuel flow ratesencountered in the operation of the engine fuel metering system in whichthe flowmeter is employed. The flowmeter calibration curve would beplotted in terms of pulses per second as ordinate and flow rate inpounds/hour as abscissa and ideally should be a linear function, y=kX,starting from zero and increasing linearly and uniformly at a constantrate which would therefore yield a straight, flat horizontal line forthe ideal linearity characteristic when plotting slope versus flow rate.

Over the range of fuel rates of from 4 pounds/hour to 110.2 pounds/hourrequired for an 8 cylinder engine, it can be seen that the flowmeterexhibits excellent linearity with a deviation of no more than ±0.2 outof 16 ordinate units yielding a linearity of within ±11/4%.

The slope ordinate of the linearity characteristic of FIG. 11 is relatedto the pulse count/second of the flowmeter, the described forms of whichprovides a relatively high pulse count of 15.5 pulses per second at aflow rate of 1 pound/hour or 155 pulses per second at 10 pounds/hour and1550-pulses per second at 100 pounds/hour. The pressure drop ordifferential between the inlet and outlet of the flowmeter is in theorder of 41/2 psi at a flow rate of 100 pounds/hour and is thereforewell within the control pump capabilities.

The above-mentioned characteristics of the flowmeter are attributed toits unique size and design predicated on the desirable properties oftangential exhaust and axial exhaust-type flowmeters which have beenjudiciously combined to provide a composite flowmeter of improvedlinearity and performance. Constructionwise, the major portion of theflowmeter consists of four parts, excluding the three cover retainingscrews and O-rings, while th complete photoelectric transducer andconnector assembly adds only seven more parts, four of which areconnector pins, to the entire flowmeter. The connector pins, coverretaining screws and plastic housing retaining stud are the onlymachined parts of the flowmeter, which, as stated, is composed of aminimum number of parts and is of inexpensive and simple construction.The flowmeter housing and its cover are each unitary die-cast elementswith the housing formed in a split mold with multiple draw slides andpins to form the various passages and pocketed cavity therein.

What is claimed is:
 1. A composite tangential exhaust and axial exhaustfluid flowmeter comprisingelongated housing means of substantiallyrectangular cross-section and having a substantially cylindrical cavitytherein, fluid inlet port means and fluit outlet port meanscommunicating with and extending generally longitudinally of saidhousing means and tangentially of said cavity, axial exhaust fluidoutlet port means including a generally arcuate shaped, elongatedslotted opening formed in said housing means and communicating with saidinlet port means to exhaust fluid axially transversely of said cavity inparallel with said tangentially extending fluid outlet port means, saidslotted opening displaced radially from the center of the cavity andlocated in a region past the tangential outlet port means in thedirection of rotation of the fluid around the cavity, and rotor meanscontained in and journaled for rotation on the geometrical central axisof said cavity and rotatable by all of the fluid admitted through saidinlet port means and exhausting from said rotor containing cavitythrough any of said tangentially extending fluid outlet port means andsaid axial exhaust outlet port means formed in said rotor containingcavity.
 2. A composite tangential exhaust and axial exhaust flowmeter inaccordance with claim 1 above wherein said tangential inlet andtangential outlet port means enter and exit from the cavity in adjacentquadrants thereof and said arcuate-shaped slotted opening is located inat least one of the remaining quadrants thereof.
 3. A compositetangential exhaust and axial exhaust flowmeter in accordance with claim1 above wherein said tangential inlet and outlet port means are locatedin the southwest and southeast quadrants of said cavity and have theirlongitudinal axes collinear to each other and wherein said slottedelongated opening is located in the northwest and northeast quadrants ofsaid cavity.
 4. A composite tangential exhaust and axial exhaustflowmeter in accordance with claim 1 above wherein said arcuate slottedopening spans and is approximately one quadrant in length.
 5. Acomposite tangential exhaust and axial exhaust flowmeter in accordancewith claim 1 above wherein said arcuate slotted opening is approximately96 degrees in length.
 6. A composite tangential exhaust and axialexhaust flowmeter in accordance with claim 1 above wherein said arcuateslotted opening is displaced radially from the center of the cavity adistance approximately one-half the radius of the cavity.
 7. A compositetangential exhaust and axial exhaust flowmeter in accordance with claim1 above wherein the area of said arcuate opening is about three to fourtimes greater than the area of the tangential inlet opening.
 8. Acomposite tangential exhaust and axial exhaust flowmeter in accordancewith claim 1 above wherein the diameter of said tangential outlet portmeans exiting from the cavity is not less than the diameter of thetangential inlet port means at its inlet to the cavity.
 9. A compositetangential exhaust and axial exhaust flowmeter in accordance with claim1 above including a cover means for enclosing the cavity with the rotorelement therein and having an arcuate-shaped elongated slotted openingtherein for exhausting fluid axially of said cavity and in a directionthrough said cover opposite that from which fluid is exhausted throughsaid arcuate slotted opening in said housing means.